Abstract
Heat-assisted magnetic recording (HAMR) is a future roadmap technology to overcome the superparamagnetic limit in high density magnetic recording. Existing HAMR schemes depend on a simultaneous magnetic stimulation and light-induced local heating of the information carrier. To achieve high-density recorded data, near-field plasmonic transducers have been proposed as light concentrators. Here we suggest and investigate in detail an alternative approach exploiting a far-field focusing device that can focus light into sub-50 nm hot-spots in the magnetic recording layer using a laser source operating at 473 nm. It is based on a recently introduced super-oscillatory flat lens improved with the use of solid immersion, giving an effective numerical aperture as high as 4.17. The proposed solution is robust and easy to integrate with the magnetic recording head thus offering a competitive advantage over plasmonic technology.
Highlights
Magnetic hard disk drive (HDD) technology is essential to majority of modern computers
Conventional perpendicular magnetic recording (PMR) is constrained by the superparamagnetic limit [1]: that is, as the bits become more closely spaced, the polarization state in one magnetic grain can change the direction of the magnetic moment in the neighbouring bits, making the stored information thermally unstable
We numerically study the performance of ONSOLs with silicon dioxide (SiO2) and gallium phosphide (GaP) immersion layers to show that the solid immersion medium assisted ONSOL is capable of producing a spot suitable for use in Heat assisted magnetic recording (HAMR)
Summary
Magnetic hard disk drive (HDD) technology is essential to majority of modern computers. HAMR uses a magnetic medium with higher thermal stability but such a medium requires stronger magnetic fields for recording These fields are higher than can be generated by existing thin-film recording transducers, so HAMR needs an external laser source to locally heat the recording regions. This temporary increase in temperature reduces the magnetic resistance of the recording material allowing data writing using a lower magnetic field. The magnetic grain in the recording medium for HAMR is generally small (typically less than 10nm) [2], it is still necessary to use a small heat spot because a spot larger than the bit size will heat neighbouring bits and erase the stored information therein. In combination with solid immersion technology, which is commonly used for high-density optical storage [15], a resolution of 50nm becomes readily achievable, better than can be achieved with a conventional lens and solid immersion
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